It Helps in building bonds with like minded people:

If you are a blogger and frequently comment on other blog posts, at some point in time the author will notice your interest in his/her blog. This helps you to build up your circle of like minded people (bloggers). You get a regular reader and also some good things to read regularly. Also helps to build up traffic in sufficient time. Shoutmeloud explains…

Constant bombarding of small comments never works. Commenting has a proper protocol, it must be something which adds to the content of the post. Or it can be a hearty acknowledgment. Criticisms are desirable if put forward in a polite manner.

It can get you a free ad slot:

AnimHut runs this great offer every month. End of every month the top commentator on the blog is awarded with a free adslot for the month. This month it is giving away two such adslots.

It helps to build backlinks:

Commenting makes an active link on the page you comment. This builds a backlink that is tracked by web crawlers if the link is dofollow type. Nowadays the search engines and ranking websites heavily depend on the backlinks to rate a website. It eventually helps to pump up your blog’s rank.